For a painting, a good finishing of coating and a good efficiency of adhesion of paint particles are required. An electrostatic painting is widely used to acquire the latter requirement in which a paint spray gun is to be charged by a first potential and the spray gun emits charged paint particles, a target to be painted is to be charged by a second potential so that the electrically charged paint particles emitted by the spray gun have a first electric force applied to them urging the electrically charged paint particles toward the target. According to the electrostatic painting, the efficiency of adhesion of particles is increased and an amount of waste particles is greatly reduced.
It is, however, that according to the electrostatic painting, a force of collision between the particles and the target is strong so that a forming of an adhesion layer is rough which results in a bad finishing of a surface. In addition, safety measures add substantially to the cost, complexity and bulk of the electrostatic painting apparatus.
The present invention is mainly directed to provide a new method and an apparatus for adhering particles to the object in which, by supplying air ions, the good finishing of coating is obtained and the efficiency of adhesion is improved.
Generally, the air ions are used to neutralize the static charges. It is well known that a high concentration of both types of air ions acts to suppress accumulations of static electricity on objects to be coated. Static electrical charges attract air ions of the opposite polarity and the attracted ions then neutralize the static charges. In a pre-painting process, a use of ionizer which produce both positive and negative ions is known. For example, a spray booth in which the air ions are introduced into a chamber to neutralize and suppress a static electric charge and prevent a dust from clinging to an object to be coated is disclosed in Japanese laid-open patent No.8-84948 and Japanese utility Model Registration No-3018050.